1. Field of the Invention
The invention relates to a method for the cooling of guide vanes in a gas turbine plant which has a compressor, at least one combustion chamber and at least one turbine. The invention relates, furthermore, to a device for carrying out the method and to a use of the method.
2. Discussion of Background
Ever-higher temperatures are employed in order to achieve an even-greater power output, and, under these circumstances, structural parts where there is a particular requirement for efficient cooling become more and more important, so that even a reduction in the cooling effect due to the clogging of part of the cooling ducts constitutes a serious risk to such a structural part. The importance of lowering the temperature in the turbine guide assembly, and here particularly at the guide vanes of the first stage, has been known for a long time. If the aim nowadays is to achieve a lowering of temperature of, for example, 400.degree. C. in the case of this structural part, efficient cooling, as well as a long service life, must be guaranteed.
When a gas turbine with steam cooling is started up, another cooling medium (for example air) is initially required, since there is still no steam available. When the steam circuit is then opened, the components to be cooled are already at operating temperature. The problem here is that the steam entrains suspended matter (rust, welding beads, condensation water droplets and other solids) deposited in the line network after a shutdown of the steam circuit and consequently may completely or partially clog the cooling ducts (film bores) which are at operating temperature. Moreover, entrained condensation water droplets may result in damage to structural parts to be cooled, since stress peaks may occur locally as a result of the thermal shock effect. Furthermore, entrained suspended matter may be deposited on the structural parts to be cooled, for example on bends of the ducts, and cause overheating there due to its insulating effect. It is apparent from the foregoing that, if possible, only pure gas should flow in the compressor outlet space (combustion chamber plenum). In order to achieve this, various measures have already been proposed, but these are very complicated.